H, K, Rb, and Li inhibit Na-dependent alanine influx across the brush border of rabbit ileum. Kinetic analysis indicates that H and K behave as competitive inhibitors of influx so that increasing the concentration of H or K in the mucosal solution is kinetically indistinguishable from decreasing the Na concentration. In addition the coupling between alanine and Na influxes is markedly reduced at pH 2.5. With the exception of H and Li, none of these monovalent cations significantly affects carrier-mediated alanine influx in the absence of Na indicating that their inhibitory effects are largely restricted to the Na-dependent fraction of influx. Increasing H concentration from 0.03 to 3 mM does not affect influx in the absence of Na but markedly inhibits influx in the presence of Na. Li significantly enhances alanine influx in the absence of Na. Ag, UO2, and La also inhibit the Na-dependent fraction of alanine influx. These findings suggest that anionic groups having a pKa of approximately 4 are involved in the interaction between Na and the alanine-carrier complex; present evidence implicates carboxylate groups however, phosphoryl residues cannot be ruled out. The previously proposed kinetic model for the Na-alanine interaction has been extended to accommodate these effects of H and other monovalent cations. The mechanistic and physiological implications of these findings are discussed.
Article|
October 01 1970
Effects of Monovalent Cations on the Sodium-Alanine Interaction in Rabbit Ileum : Implication of anionic groups in sodium binding
Raymond A. Frizzell,
Raymond A. Frizzell
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania 15213
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Stanley G. Schultz
Stanley G. Schultz
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania 15213
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Raymond A. Frizzell
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania 15213
Stanley G. Schultz
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania 15213
Received:
March 16 1970
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1970 by The Rockefeller University Press
1970
J Gen Physiol (1970) 56 (4): 462–490.
Article history
Received:
March 16 1970
Citation
Raymond A. Frizzell, Stanley G. Schultz; Effects of Monovalent Cations on the Sodium-Alanine Interaction in Rabbit Ileum : Implication of anionic groups in sodium binding . J Gen Physiol 1 October 1970; 56 (4): 462–490. doi: https://doi.org/10.1085/jgp.56.4.462
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